1. Field
One or more embodiments described herein relate to a semiconductor device.
2. Description of the Related Art
Various processes are used to manufacture a semiconductor device. These processes include a deposition process, an ion implantation process, a photolithography process, a cleaning process, and a polishing process. These processes may be repeatedly performed to form a plurality of semiconductor devices on a wafer.
More accurate thickness measurements are required as the patterns in a semiconductor device become finer. One approach for measuring thickness involves radiating light and/or a sound waves to a specimen and detecting changes in the light and/or a sound waves. However, errors may occur in specific cases using this approach.
Another method known as spectroscopic ellipsometry (SE) uses an ultraviolet (UV) rays. In this method, thickness is measured based on changes in the phase of polarized light on a measurement target layer of a specimen. The SE method has a high resolution capable of measuring thickness in the range of several angstroms (Å).
In implementing the SE method, an optical constant value of the measurement target layer may be expressed as a mathematical function. A change in polarized light by the measurement target layer is then divided into components such as a thickness, a dispersive term, and an absorptive term.
However, the SE method has drawbacks. For example, some materials to be measured are difficult to express by a specific function. Additionally, light change conditions of thin layers of a multi-layer having a complex structure may be similar to each other. Thus, correlation between the thin layers may be high. As a result, it may be difficult to measure accurate thickness of a multi-layer having the complex structure using the SE method.
Furthermore, in manufacturing processes of semiconductor devices, a composite layer may be complex, a new material may be applied to a single layer, and/or physical properties of thin layers may be greatly changed by new processes. Thus, it may be difficult to accurately measure thickness of a thin layer.